Rotation rate sensors are usually used to sense the angular speed of a system about at least one defined axis. An important field of application of rotation rate sensors is motor vehicle engineering, for example in vehicle movement dynamics control systems such as the electronic stability program (ESP) or what is referred to as a rollover detection means. Such safety-critical fields of use make special requirements of the rotation rate sensors in this context.
The document U.S. Pat. No. 6,230,563 B1, which is incorporated by reference, describes a z axis rotation rate sensor which can therefore sense a rotation rate about its z axis, wherein the base surface of its substrate is oriented parallel to the x-y plane (Cartesian coordinate system). This rotation rate sensor has two seismic masses which are coupled to one another by means of a coupling bar, wherein the coupling bar is suspended from a torsion spring on the substrate. The seismic masses are suspended directly from the substrate, wherein this suspension means is embodied in such a way that it has to ensure the deflection capability of the seismic masses both for the drive modes and for the reading modes of the rotation rate sensor, as a result of which undesired crosstalk between the two oscillation modes can occur, and this has an adverse effect on the measurement.
Document WO 2006/034706 A1, which is incorporated by reference, proposes suspending the seismic masses from a frame which is itself suspended from the substrate. As a result, degrees of freedom in the suspension can be restricted to the extent that, for example, the frame structure oscillates together with the seismic masses in the drive mode, but in the reading mode only the seismic masses oscillate, as a result of which crosstalk between the two oscillation modes can be largely avoided. However, the coupling of the seismic masses by means of the proposed coupling unit is sensitive to interference excitations oriented in the same direction in the measuring direction, such as, for example, tremors.
Micromechanical springs are known for suspending seismic masses in rotation rate sensors, which springs bring about deflections in the reading direction due simply to relatively small preparation inaccuracies which lead, in particular, to undesired edge angles of the respective structures, without a rotation rate being present in the drive mode. This generates interference signals which are possibly evaluated as rotation rate signal components and therefore falsify the rotation rate signal or cause a measuring error with respect to the rotation rate signal.
Such undesired edge angles or tilting of springs are process-induced and can be avoided only to a restricted degree. The interference signals described above, which do not arise due to a sensed rotation rate but rather due to incorrect deflections in the reading direction as a function of the deflection of the seismic mass and the springs thereof in the driving direction, are also referred to as quadrature signals or quadrature.